Introduction to Dfs Limits of Dfs • 260 characters per file path • 32 alternatives per volume • 1 Dfs root per server • Unlimited Dfs roots per domain • Volumes limited by system resources Overview of Dfs Roots • The Dfs Service is auto-installed with the installation of Microsoft Windows 2000 Server. • Two types of Dfs roots can be configured on Windows 2000 Server computers: stand-alone and domain. Stand-Alone Dfs Roots • Stand-alone Dfs information is stored in the local registry. • A stand-alone Dfs root permits a single level of Dfs links. • When the Distributed File System snap-in is used to connect to existing stand-alone Dfs roots, all servers known to the browse list are retrieved because there is no unique NetBIOS name registered by Dfs-enabled servers. • Stand-alone Dfs roots can be located on all supported file systems, although locating resources on NTFS-formatted partitions is recommended. • Stand-alone Dfs roots offer no replication or backup; the Dfs root represents a single point of failure. Domain Dfs Roots • Multiple servers hand out referrals for the Dfs namespace. • A fault-tolerant Dfs root is stored in Active Directory services and is replicated to every participating Dfs root server. Changes to a Dfs tree are automatically synchronized with Active Directory services. • Fault-tolerant roots must be located on NTFS version 5.0– formatted partitions. • The list of domains and servers is populated by querying the global catalog for all fault-tolerant Dfs roots. • Dfs replication topology uses the existing Active Directory replication topology. Configuring a Stand-Alone Dfs Root • Stand-alone Dfs stores the Dfs topology on a single computer and does not provide fault tolerance. • A stand-alone Dfs root is physically located on the server that users initially connect to. • To create a stand-alone Dfs root, use the Distributed File System snap-in to start the New Dfs Root wizard. Creating a Stand-Alone Dfs Root Configuring a Domain Dfs Root • Domain Dfs writes the Dfs topology to the Active Directory store, which allows links to point to multiple identical shared folders for fault tolerance. • Domain Dfs supports DNS, multiple levels of child volumes, and file replication. • To create a domain Dfs root, use the Distributed File System snap-in to start the New Dfs Root wizard. Configuring New Dfs Links • Users can browse folders under a Dfs root without knowing where the referenced resources are physically located. • After you create the Dfs root, you can create Dfs links. • To create a Dfs link, use the Distributed File System snap-in to open the Create A New Dfs Link dialog box. Creating a Dfs Link Dfs Links FRS Replication • FRS is installed automatically on all Windows 2000 Server computers. • FRS is configured to start automatically on all domain controllers and manually on all stand-alone and member servers. • The Active Directory store uses FRS to synchronize the directory among all the domain controllers. • Active Directory services automatically generates a ring topology for replication among domain controllers in the same domain. • The ring structure ensures that there are at least two replication paths from one domain controller to another. Site and Domain Structures • A site is made up of one or more IP subnets that identify a group of well-connected computers. • Domain structure and site structure are maintained separately in Active Directory services. • A single domain can include multiple sites, and a single site can include multiple domains. Single Domain with Single Site Single Domain with Multiple Sites Multiple Sites with Multiple Domains Intra-Site Replication • Intra-site replication occurs between domain controllers within a site. • Replicated data is not compressed. • The default replication interval is five minutes. • Replication is trigger-based (notification and pull). Inter-Site Replication • Inter-site replication occurs between domain controllers in different sites. • You can specify the time when inter-site replication should occur. The default replication interval is three hours. • You can specify the network transport for use in inter-site replication. • Inter-site replication is compressed, regardless of the transport used. • Inter-site replication compression reduces the data on the network by 88 to 90 percent. • Inter-site replication is not configured automatically; it must be configured by an administrator. Knowledge Consistency Checker (KCC) • The KCC generates a ring topology for replication among domain controllers in the same domain. • The ring structure guarantees that there are at least two replication paths from one domain controller to another. • The KCC analyzes the replication topology within a site to ensure that the replication topology is efficient. Unique Sequence Numbers (USNs) • When a directory object is updated at a domain controller, a USN is assigned. • When the domain controller writes the change into the directory, it also writes the USN. • Each domain controller maintains a table of the USNs that it receives from every other domain controller in the domain. • USNs eliminate the need for precise time stamps for changes. • USNs simplify recovery after a failure. Replicating SYSVOL • Changes to the %systemroot%\SYSVOL folder on any domain controller are automatically replicated to other domain controllers within the site. • The replication topology and process are separate but identical to Active Directory replication. • Windows 2000 Server sets up a default folder structure for SYSVOL. Replicating Dfs Fault-Tolerant Roots • Dfs and file replication support a number of features. • Each Dfs root or link can reference a replicated set of share consequences. • Dfs replication is disabled by default; use the Distributed File System snap-in to enable replication. Configuring FRS for Inter-Site Replication • Use the Active Directory Sites And Services snap-in to configure inter-site replication. • To configure the FRS settings, you must create a new site link for the inter-site transport protocol listed in the console tree.